Room with a View

When the Perlmeister is on the road, he likes to know what's going on at home. Armed with just two scripts, he draws on the Tumblr API to store snapshots cyclically from his home security camera.

When I'm traveling, knowing that my home is threatened neither by fire nor by an invading band of thieves contributes greatly to my sense of well-being. To avoid phoning my neighbors to satisfy my security cravings, I installed a panning camera to keep a watchful eye on the skyline of San Francisco through my living room window (Figure 1). The Foscam FI 8910W [1], which costs about US$ 60 and includes a WiFi connection, supports remote control via the Internet and lets me stream the video to my mobile phone – no matter where I happen to be.

Figure 1: The panning Foscam camera in the Perlmeister's living room watches over downtown San Francisco.

Quirky Camera

Before you indulge in impulse purchases, be warned: The cheap Foscam camera has some annoying quirks. For example, when it's dark, the camera always turns its infrared LED ring on after rebooting, which happens every now and then for some unknown reason. This feature sounds useful at first, but if the camera is set up directly in front of a reflecting window, the whole thing turns into a fiasco, with the camera dazzling itself until someone notices and switches off the infrared ring by hand.

Thus far, customers have waited in vain for a firmware update that rescues them from this feature. "You get what you pay for," as people say laconically here in the US. Also, the camera's web interface looks like a relic from the last century: Users are given a jerky video stream and can use the control buttons at the top left to pan the camera head about 300 degrees laterally and tilt 120 degrees upward (Figure 2).

The fact that the built-in Foscam server wants you to supply your password in plain text via HTTP instead of via HTTPS is another faux pas that rational users will tend to counteract with a VPN if they need to transmit images over the Internet.

If your camera is set up at home and you want to access it from the outside, your router's firewall will need to use port forwarding to forward the incoming requests. Because the camera works with a dynamic DNS service, the web interface is always accessible at the same URL, such as http://<XXX>.myfoscam.org:5148, independent of the dynamically assigned WAN IP.

On My Mark – Blog!

Because I happen to own the camera, I have to try to make the best of it. One of my first conclusions is that it makes more sense to grab snapshots regularly with the camera and dump them onto the Internet, instead of dialing up the camera periodically to make sure everything is okay. A script can then line up the still images on a web page – and one look is all it takes for a daily routine check. So, that is exactly my plan for this month's Perl column.

To help me in this noble cause, I noticed that the Tumblr microblogging platform, which my employer, Yahoo, acquired about six months ago, has a programmable API [2]. A quick check on CPAN showed that avid open source programmers had already published a matching Perl module named WWW::Tumblr. The rest was clear sailing: A cron job executes the script presented in Listing 2 several times a day and grabs a snapshot with the camera.

The script then routes the image via the API to my Tumblr blog, which shows the messages in reverse chronological order and offers all kinds of social platform bells and whistles such as Like buttons or reblog functions (Figure 3). Because most Tumblr users follow several blogs, you can add the sequence of home security images to your follow list and consume them along with other postings (Figure 4).

Figure 3: Each time the tumblr-post script is called, a still image from the camera is added to the Tumblr blog.

Figure 4: Once the blog has been added to your follow list, its postings appear in your stream with other publications.

OAuth Grants Access to Tumblr Blog

For the tumblr-post Perl script to be allowed write access to a user's blog automatically, you need to register it as a Tumblr application. Additionally, the user needs to grant the application appropriate rights. These steps are described in Tumblr's API documentation [2].

Figure 5 shows the registration process for the Perlsnapshot test application, and because it is a script – and not an app for the iPhone or an Android device – I have left the App Store URL and Google Play URL fields blank.

Figure 5: After registering the application …

The Default callback URL, that is, the Web address that Tumblr invokes with the generated access tokens after authorization by the user is http://localhost:8082 (Figure 6). As an application icon, I just uploaded a 128x128 pixel self-portrait.

Figure 6: … and specifying the callback URL…

After clicking on Register below the completed form, Tumblr shows you a consumer key and a secret key (Figure 7). These two hex strings identify a registered Tumblr application, which in turn is allowed to ask users for access rights.

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